Air-lift boat



J 1964 R. w. TIBBETTS EI'AL 3,137,262

AIR-LIFT BOAT Fiied Sept. 50, 1960 2 Sheets-Sheet 1 INVENTORS @272022411. 22665!!! Jan M1 3. Jam er M June 16, 1964 3,137,262

R. w. TIBBETTS ETAL AIR-LIFT BOAT Filed Sept. 50, 1960 2 Sheets-Sheet 244 10 1 a 7 4 J0 J \HK United States Patent 3,137,262 AIR-LIFT BOATRaymond W. Tibhetts and Joseph A. Sawyer, Camden, Maine, assignors toTibbetts Industries, Inc., Camden, Maine, a corporation of Maine FiledSept. 30, 1960, Ser. No. 59,560

Claims. (Cl. 114-67) This invention relates to the hull construction ofa boat or other vehicle and more particularly to a means for reducingthe surface drag of water against a boats hull. One attempt to eliminatethis drag has been to cause the greater part of the boats weight to besupported by air pressure in the form of an air cushion containedbeneath the hull. However prior attempts at this form of constructionhave met with difiiculty in making the boat stable and in containing theair cushion without unduly hampering the boats normal operation. Thisproblem with stability is that, as one portion of a boat supported on anair cushion is depressed, no more water is displaced under thedepressed. portion than elsewhere and thus no restoring force isproduced.

Accordingly objects of the present invention are to provide a boat orother vehicle which has minimum friction with the underlying water orother'medium, which is automatically stabilized against roll and pitch,which is simple and economical in construction and which is durable andreliable in use.

In one aspect the invention contemplates a hull having sides and abottom, fins projecting downwardly-along opposite sides of said hull toform an air space therebetween, means substantially bridging saidfins-to close the ends of said space, said bottom having an elongateslot extending lengthwise of the hull inboard of each of said fins,

the mouth of each slot being disposed above the level of the lower edgesof said fins and aimed laterally outward toward the corresponding fin,and means for projecting a curtain of air through each of said slots.

In the preferred embodiment the aforementioned air space is divided intosections by partition means and the vehicle comprises means responsiveto the attitude of said hull for regulating the flow of air into eachsection relative to the flow into the other sections.

A more complete understanding of the present invention may be obtainedfrom the following detailed description of the preferred embodimentshown in the accompanying drawings in which FIG. 1 is a plan view of anair-lift boat according to the present invention;

FIG. 2 is a rear elevation of the boat of FIG. 1;

FIG. 3 is a section on the line 3-3 of FIG. 1;

FIG. 4 is a section on the line 4-4 of FIG. 1;

FIG. 5 is a section on the line 55 of FIG. 1;

FIG. 6 is a broken away side elevationof the boat of FIG. 1; and

FIG. 7 is a bottom view of theboat of FIG. 1.

Referring now to the drawings, the boat has a hull includingsides 1,bottom 2, how 3, and stern 4. In the preferred embodiment the bottom 2comprises a thick layer of a highly buoyant substance 10 such as aclosed cell plastic which renders the boat substantially unsinkable.

Pins 5 depend from each side of the hull and extend 3,137,262 PatentedJune 16, 1964 along its entire length thereby defining an air spaceheneath the hull. The ends of this air space are closed by pivoted vanes7 and 8 which depend from the bow 3 and the stern 4 respectively. Theforward Vane is segmented and each segment 17 is freely pivoted at itsupper edge 18 so that the vane as a whole may tend to conform itself tothe surface of the water over which the boat passes. A stop 19 isprovided to limit the forward travel of the segments 17 and the airpressure beneath the boat tends to keep the segments in their mostforward position. The rear vane 8 is connected by the crank 20 and therod 21 to a lever 22 within the cockpit so that its attitude may beadjusted while the boat is running.

The sides 1 of the hull and the panels 34 define ducts 33 extendingalong each side of the hull for its entire length. A blower31 is open tothe atmosphere through the intake 30 and is directed by the tubular duct29 into the cross duct 32 defined by the panels 28 and 27.

This cross duct 32 connects at either end with one of the side ducts 33and damper valves 36 and 37 at each of these intersections determine therelative amounts of air passing to the bow and stem parts of each of theside ducts. I

The fins 5 may be hollow, connect with the side ducts 33 as shown inFIG. 5, and terminate in an inwardly directed outlet 11. A set of slots12 directedlaterally outward depend from the bottom of the hull atpoints beneath the inner wall 34 of each of the side ducts 33, the mouthof each of these slots being disposed above the level of the lower edgesof the fins 5.

A bow cross-duct 40 connects the two side ducts 33 at a point just aftof the segmented bow vane 7 and vent 41 extending through the bottom 2of the boat connects this how cross-duct 40 with the air space beneaththe hull. Approximately midway between the bow and the stern a partition43 depends from the bottom 2 of the hull dividing the air space betweentwo sections. A second cross-duct 44 connects the side ducts 33 just aftof this partition 43 and is also open to the air space through a vent45. Scoops 50 and 51 depend from the bottom of the boat at points nearthe how 3 and stern 4 respectively.

These scoops are connected by tubing 53, each to one side of adouble-acting hydraulic cylinder 54. The piston 55 of. the hydrauliccylinder 54 is connected by rods 56 and 57 and cranks 58 and 59 to thedamper valves 36 and 37.

When the blower 31 is started air is forced under the hull through theslots 12, the outlet 11, and the vents 41 and 45, lifting the boat andforming an air cushion in the space between the fins 5; As the outlet 11at the sides of the boat are inwardly directed, they cause an aircurtain to be formed which will tend to contain the air cushion beneaththe hull even if a fin 5 is momentarily pulled completely clear of thewater as by a wave striking the boat.

In order to maintain stability even though the sides 1 or outlet 11 aresubmerged the preferred embodiment has a set of elongate slots 12running parallel to the sides of the boat and directed laterallyoutward. Normally these slots lie close to the bottom 2 of the hull sothat they will remain clear'of the surface of the water while the 'sternsections of the air space.

zones of higher pressure along the sides between the slots 12 and thefins 5. As each narrow slot 12 is supplied with air through its ownseparate side duct 33, which duct is of large capacity as compared withthe air needed by the slot, the amount of air passing through each slotis, at any given moment, largely unaffected by the amount of air takenby the other slot and thus the Zones of higher pressure are for the mostpart independently supplied with air and tend to make the boat stablebecause the effectiveness of the air curtain is increased as the air jetnears the surface of the water. Thus as one side is depressed the zoneon that side increases in pressure creating a correcting force.Conversely, the zone on the opposite side tends to spill some of itscontained air into the space under the center of the boat thus aidingthe righting action.

It has been found for a boat 16 feet long and 8 feet wide having sidefins terminating in /2 inch outlets directed inwardly at 39 from thevertical and opening 5 inches below the bottom and having outwardlydirected A inch slots depending from the bottom and running parallel tothe sides at a distance of 18 inches therefrom, each of said slots andoutlets communicating with a source of air under a pressure ofapproximately 5 inches (water gauge), that when one side of the boat isdepressed 2 inches there is a pressure increase in the zone between theopposed slots of one inch .(water gauge) developing a lifting force onthat side of 120 lbs.

In order to obtain fore-aft stability the preferred embodimentincorporates an automatic device for controlling the relative quantityof air supplied to thebow and the Two scoops and 51 provide the sensingfor this device. When the boat is under way and is on a level keel bothscoops are out of the water. As the boat pitcliesione or the other scoopcomesinto contact with the surface of the water creating a hydraulicpressure which is transmitted by tubing 53 to one side of the piston 55of a double acting hydraulic cylinder 54. If the boat is proceeding at15 miles per hour the scoop will produce a hydraulic force ofapproximately 5 pounds per square inch. Higher speeds will producecorrespondingly higher pressures and the area appropriate for the piston55 may be calculated accordingly; The cylinder, acting through the rods56 and 57 and the cranks 58 and 59 moves the damper valves 36 and 37which regulate the quantity of air going to the part of the boataffected in such manner as to correct thepitching condition. The cranks58 and 59 and the rods 56 and 57 are connected in a non-symmetricalfashion so that the pneumatic forces created by the movement of thedamper valves on either side will be aiding. The partition 43 extendingfrom side to side and depending from the bottom at a point approximatelymidships allows a pressure differential to be maintained between bow andstem and prevents such a rush of air from one end to the other as wouldnullify the balancing action. Although the supply of air to the slots 12and the outlets 11 is also subject to regulation by the damper valves 36and 37 the major sources of air for this dynamic balancing are the bowand midships cross-vents 41 and 45 respectively.

Obviously, it would also be possible to employ a very similar device toachieve lateral stability. In such a case 7 scoops would be placed atpoints on opposite sides of the hull and an additional fin would be rundown the middle of the hull so as to split the air cushion into twoindependent sections.

In the preferred embodiment the front vane 7 for con taining the aircushion is segmented so that individual segments 17 may yield to theimpacts of waves without I causing a general escape of air pressure.These flap segments 17 are freely, suspended from their upper edges witha stop 19 to limit their forward travel. The contained air pressureprevents the flaps from swinging too far to the rear. As an' alternativeconstruction the front flap may be constructed of a semi-pliablematerial such as plastic. The stern vane 8 is arranged so that itsattitude may be set by a lever 22 within the cockpit of the boat. Thislever may then be set according to the blower capacity and the speeddesired. At higher speeds the capacity of the blower is greatlyincreased by the ram eflect of the boat moving through the air and thusthe rear vane 8 may be opened entirely, so as to clear the water,further reducing the water drag.

It should be understood that this disclosure is for the purpose ofillustration only and that the present invention includes allmodifications and equivalents falling within the scope of the appendedclaims.

We claim:

1. A vehicle comprising a'hull having sides and a bottom, finsprojecting downwardly along opposite sides of said bottom to form an airspace therebetween, each of said fins being hollow and terminating in aninwardly directed outlet, means substantially bridging said fins toclose the ends of said space, said bottom having an outwardly directedelongate slot extending lengthwise of the hull inboard of each of saidfins, the mouth of each said elongate slot being disposed above thelevel of the lower edges of said fins, and means projecting a curtain ofair through each of said slots and through each of said outlets. 1

2. A vehicle comprising a hull having sides and a bottom, finsprojecting downwardly along each side of said bottom to form an airspacetherebetween, said fins being hollow and terminating in inwardlydirected outlets, said bottom having an outwardly directed elongate slotextending lengthwise of the hull inboard .of each of said 'fins, themouth of each said outwardly directed slot being disposed above thelevel of the lower edges of said fins, means for projecting a curtain ofair through each of said outlets and slots, means substantially bridgingsaid fins to close the ends of said space, partition means substantiallybridging saidfins for dividing said space into a bow section and a sternsection, and means responsive to the attitude of the hull for regulatingthe flow of air to each section relative to the other section.

3. A vehicle comprising a hull having a bottom, means projectingdownwardly from the bottom around its periphery to form an air space, apartition dividing said air space into sections, means for forcing airunder pressure into each of said sections, forwardly directed scoopsprojecting below said bottom in each of said sections, and meansresponsive to the flow of water through said scoops for controlling thesupply of air to each section relative to the other section thereby tomaintain the hull on an even keel.

4. 'A vehicle comprising a hull having sides and a bottom, finsprojecting downwardly along opposite sides of said bottom to form an airspace therebetween, means substantially bridging said fins to close theends of said space, said bottom having an elongate slot extendinglengthwise of the hull inboard of each of said fins, and means forprojecting a curtain of air through each of said slots, said slots beingarranged with the mouth of each slot being disposed above the level ofthe lower edges of said fins and adjacent the plane in which asupporting surface will lie and being oriented so that the curtain ofair projected therethrough sweeps laterally outwardly over thesupporting surface thereby to create a pressure gradient within the .airspace and maintain independent zones of higher pressure between eachslot and the corresponding fin.

.- 5. A vehicle comprising a hull including sides and a bottom, meansfor maintaining an air cushion beneath said hull, and air jet means onsaid bottom for directing laterally sweeping air jets relative totheplane in which a supporting surface will lie in such a manner as tocreate pressure gradients within said air cushion, said air jet meansarranged so as to define substantiallyindependent zones of higher airpressure beneath various sections of said hull, the pressure within eachof said zones depending upon the proximity of the corresponding portionsof said air jet means to the supporting surface.

References Cited in the file of this patent UNITED STATES PATENTSDinesen Aug. 19, 1913 Ryan et al. Oct. 19, 1915 Dunajeif Apr. 18, 1922Casey Mar. 22, 1927 Warner Aug. 18, 1931 Cristadoro June 29, 1943Brinkema Jan. 15, 1952 OTHER REFERENCES Flight, Issue of Sept. 11, 1959(page 197 relied on).

1. A VEHICLE COMPRISING A HULL HAVING SIDES AND A BOTTOM, FINSPROJECTING DOWNWARDLY ALONG OPPOSITE SIDES OF SAID BOTTOM TO FORM AN AIRSPACE THEREBETWEEN, EACH OF SAID FINS BEING HOLLOW AND TERMINATING IN ANINWARDLY DIRECTED OUTLET, MEANS SUBSTANTIALLY BRIDGING SAID FINS TOCLOSE THE ENDS OF SAID SPACE, SAID BOTTOM HAVING AN OUTWARDLY DIRECTEDELONGATE SLOT EXTENDING LENGTHWISE OF THE HULL INBOARD OF EACH OF SAIDFINS, THE MOUTH OF EACH SAID ELONGATE SLOT BEING DISPOSED ABOVE THELEVEL OF THE LOWER EDGES OF SAID FINS, AND MEANS PROJECTING A CURTAIN OF